1. Field of the Invention
This invention relates to internal combustion engines and more particularly to a piston ring for use in such engines.
2. Prior Art
Recently, more emphasis has been placed upon controlling internal combustion engine emissions. It has been determined that a significant quantity of undesirable emissions as well as power loss are the result of combustion blowby. Such blowby occurs between the outer diameter of the piston and the cylinder wall. While compression rings, carried by the piston in ring grooves, have been used to seal this space, the prior art rings and ring sets do not completely seal the firing chamber.
Blowby can still occur between the outer diameter of the piston ring and the cylinder wall, or by a gas flow around the piston ring in the ring groove. It has been suggested to overcome the first form of blowby by placing expansion springs in the ring groove to force the piston ring into tighter contact with the cylinder wall. Such expansion springs, while helpful, increase the friction of the piston ring against the cylinder wall at all times by applying a continuous pressure to the inner diameter of the piston ring.
It has been further suggested that the piston ring be made substantially L-shaped, as in the U.S. Pats. to R. S. Moore, No. 1,159,066 and Goetze, No. 2,844,424, with one leg of the L engaging the cylinder wall while the other leg is retained in the ring groove. In such constructions, the force of the entrapped combustion gases is used to expand, circumferentially, the first leg into tighter engagement with the cylinder wall. While such rings may be effective in reducing blowby between the ring and the cylinder wall, they are not effective in preventing the escape of such gas through the ring groove. Further, because such rings are historically of split annular construction, a considerable amount of gas can escape in the area of the ring gap.